This application relates to a quick connect fluid coupling which ensures that a tube is not sealed unless the tube is fully inserted into a connector structure.
Quick connect fluid couplings are well known in the art and used to quickly connect a tube to a housing or second tube. Several quick connect couplings are utilized in most modern vehicles to connect brake lines, air conditioning lines, power steering lines and other high pressure lines to a housing, or second tube.
A particularly successful prior art coupling consists of a spring or retainer received within a female housing bore. The retainer has a plurality of arms which extend radially inwardly in a direction moving axially into the bore. The tube has a radially greater upset portion which moves into the bore and abuts an inner peripheral surface of the arms. The axially and radially innermost ends of the arms define an inner diameter approximately equal to the outer diameter of the tube at locations other than the upset portion. As the tube is inserted further into the bore, the upset portion forces the arms radially outwardly, and moves axially past the arms. Once the upset portion has moved axially beyond the arms, the arms spring back to a position where they are radially outwardly of the tube, and axially between the upset portion of the tube an outer end of the bore. The tube is then fully inserted, and the retainer securely retains the tube within the housing.
In one prior art coupling, the retainer is of a so-called "avalanche" type where the force required to insert the tube into the housing is at a first relatively low point for initial axial insertion, and then rises sharply to a relatively high point after the upset portion initially contacts the inner periphery of the arms. The point where this high required force begins is defined as an "avalanche" point. Once an operator has supplied sufficient force to overcome this high required force, the momentum carries the tube further axially inwardly and ensures that it is fully inserted.
Problems are sometimes encountered with this type of quick connect coupling since a tube inner end is at an axial position where it is aligned with seals in the housing prior to reaching the avalanche point. The seals engage the outer periphery of the tube and provides some resistance to further insertion of the tube. This may give a false impression or feel to the assembler that the high required force may have been overcome. Thus, the prior art has sometimes resulted in an assembler misinterpreting this feel as an indication that the tube is fully inserted. Further, if an assembler neglects to fully insert the tube for whatever reason, it is still possible that the prior art couplings will provide a seal between the tube and the housing.
It is undesirable for the tube not to be fully inserted since it could become disconnected in use. This is particularly true when the tube is used in a vehicle. With the prior art structure discussed above, should the tube not be fully inserted within the housing, a seal may still be provided between the housing and the tube. The seal may be adequate for a period of time until the vehicle has driven off the assembly line and away from the factory. The fluid pressure in the line, vibration or temperature cycling, will eventually cause the tube to become disconnected from the housing. It is far more preferable for the improper connection to be identified before the vehicle leaves the assembly line.